Recorder circuit



Nov. 6, 1956 F. w. CRAWFORD RECORDER CIRCUIT 3 Sheets-Sheet 1 Original Filed Sept. 29, 1950 F/GIl.

uwmnm F.W. CRAWFORD HMLW J Nov. 6, 1956 ,F. w. CRAWFORD RECORDER CIRCUIT OriginafFiled Sept. 29, 1950 3 Sheets-Sheet 2 FIG. 3.

Elm lEic INVENTOR. F. W. CRAWFORD HML 47 lam 13c AM ORNZS FIG. 5.

Ndv. 6, 1956 F. w. CRAWFORD RECORDER CIRCUIT 3 Shets-Sheet 3 Original Filed Sept. 29, 1950 RECORDER AMPLIFIER INVENTOR. F.W. CRAWFORD BY mm 7 United States Patent 2,769,919 RECORDER CIRCUIT Francis W. Crawford, Idaho Falls, Idaho, assignor to Phillips Petroleum Company, a corporation of Delaware Original application September 29, 1950, Serial No. 187,600, now Patent No. 2,724,307, dated November 22, 1955. Divided and this application May 28, 1953, Serial No. 358,107

11 Claims. (Cl. 250-835) This invention relates to apparatus for analyzing a desired process or sample stream. In one specific aspect it relates to apparatus for adjusting the sensitivity and range of recording apparatus.

This application is a divisional application of my co pending application, Serial No. 187,600, filed September 29, 1950, now Patent 2,724,307.

Heretofore, considerable difficulty has been experienced in providing a simple, reliable mechanism for ation of heat supplied to the column, the reflux ratio, the

In fact, the apparatus of my invention is useful in either indicating or auto- Figure 1 is a top vention;

Figure 2 is a bottom view Figure 3 is a detail view eter cell together with a portion of the temperature and pressure regulating device;

Figure 4 is a schematic circuit diagram of the refractometer;

view of the refractometer of my in- 2,769,919 Patented Nov. 6, 1956 Figure 5 is a vertical sectional view of a modified form of refractometer cell;

Figure 6 is a schematic view of an optical system utilizing the cell of Figure 5; and

Figure 7 is a schematic circuit diagram of a modified photoelectric cell circuit.

Referring now to Figure 1, the apparatus includes a which is proportional to the difference in refractive inden of the two fluids contained therein. After leaving the cell 13, the beam is reflected by a movable mirror it is centered upon the dual detector assembly 14 necessary to 12a at one end connected to tube and having a colparent that the bellows 12 serves as an ad ustable coupling between the source 11 and the cell A lens 13b, Figure 3, which is mounted mounted between block 13 and an annular member 13f, this Window also being provided with a scaling is secured to block tached to block 13 by a plurality of screws, one of which is shown at 1312. The blocks 132 and 13) have interfitting portions 130 so that, when they are assembled, a rigid unitary structure is formed.

A diagonal transverse plate 13p of transparent material is mounted between the blocks 13! and a valved outlet conduit of slightly greater diameter, is conduit 13v and a valved outlet 13a while chamber 13s, provided with an inlet conduit 13w.

leaving the cell through window 113i .and passing to the movable mirror assembly 14. If the refractive index of the liquids in the two cells is identical, the beam leaves the cell in an axial path but, if the refractive index of the liquids diifers, the beam is deviated from its axial path by an amount proportional to the difference in refractive index between the two liquids. Instead of containing a standard liquid, the chamber 13r can contain any other fluid with which it is desired to compare the refractive index of a process stream or other streams to be analyzed. For example, a second process stream can be passed continuously through cell 13r and the deviation of the beam from its axial path is then continously proportional to the difference in refractive index between the two streams.

' It is important that a close control of temperature and pressure of the cell 13 be maintained, particularly when visible radiation is utilized, although control of these conditions is also important when ultra-violet, infra-red or other types of radiation are used. In order to regulate "the pressure, that is, to maintain the same pressure in the two chambers 13r and 13s, I provide an equalizing device 18 formed from a tubular piece 18a of metal defining an interior chamber 13b having a threaded opening 18c therein into which the conduit 13v is fitted, this chamber also communicating through a bore 18d and a nipple or'fitting 18e with a valved conduit 18 Accordingly, the pressure within chamber 18b is the same as that in chamber 13s. Mounted in the chamber 18b is a bellows 18g which communicates through a bore 18h and a coupling 181' with a valved inlet conduit 18 The interior of the bellows also communicates by a bore 18k and a fitting 18m with the inlet conduit 132? of chamber 13r. As a result, the pressure interiorly or the bellows 18g is the same as that existing in chamber 13r. It will be apparent that the bellows 18g expands or contracts, thereby changing the relative volumes of the chambers 18h, 13r and 18b, 13s until the pressures therein are equal. Only a small variation in pressure ordinarily need be compensated for by the equalizer 18 and it functions in a very sensitive manner to equalize the pressures in the two chambers.

Temperature control of the cell unit 13 is effected by forming the blocks 13c, 13 from a metal which is a good conductor of heat and by making these blocks sufficiently massive to serve as a reservoir thermally contacting the chambers 13; and 13s. In this connection, it will be noted that increases or decreases in the temperature of the cell as a whole does not have any substantial effect upon the bending of the beam passing through the cell. However, even a small temperature variation between the fluids in the two cells may result in errors. Thus, the described construction of unit 13, while it does not eliminate temperature variations of the whole cell, provides eflicient heat transfer characteristics such that the fluids in the two cells remain at almost exactly the same temperature.

A further improvement in the described temperature control is effected by the material to be analyzed through a conduit 19a which in turn passes through a rather large storage vessel 1% and, thence, through the conduit 18 and the pressure equalizer 18 to cell 13r. Even rather large variations in the temperature of the fluid entering through line 19a produce only small changes in the temperature of the entire body of liquid within the vessel 1% with the result that the temperature variations in fluid fed to the cell unit are very small. These small variations in temperature of the fluid in chamber 13r are readily transferred to the fluid in chamber 13s by the efficient heat transfer construction of the cell with the result that the two bodies of fluid remain accurately at the same temperature. This contributes materially to the accuracy of the analysis performed by this apparatus.

Large temperature variations are also prevented by the coil 11b which carries away most of the heat produced by the source 11 and by metal tubing 20 which is disposed in a sinuous path at the underside of the base 10, cooling fluid being circulated through this tube from an inlet conduit 20a and passing through the tube to an outlet conduit 20b. This tends to maintain the base, and thereby the cell unit 13, at a constant temperature.

Referring now to Figure 1, the movable mirror assembly 14 includes a base 14a which is pivotally mounted at 1417 to the base 10, the base 14a carrying a bracket 14c to which a plane mirror 14d is adjustably secured by screws 146, these screws permitting angular adjustment of the mirror, as desired. integrally formed with the base 14a is an elongated cam follower arm 14 carrying a cam roller 14g which is urged into engagement with a cam 21a by a spring 14h. The stationary mirror assemblies 15 and 16 include brackets 15a and 16a, respectively, which are secured to the base 19 by screws 15b and 16b, these brackets carrying the respective mirrors 15c 160, which are secured thereto by adjusting screws 15d and 16d.

The dual detector unit 17 includes a bracket 17a secured to the base 10 by screws 17b, this bracket having a casing 17c secured thereto by adjusting screws 17d. Where visible light is utilized as the radiation for purposes of analysis, the casing 17c includes two photovoltaic cells 17e, 17 mounted within an insulating sleeve 17;; which, in turn, is supported within the casing 17c. These cells are symmetrically disposed with respect to the beam of radiation reflected thereon from mirror 160, mirror 15c and mirror 14a. Where infra-red radiation is utilized, the cells are replaced by bolometers or other suitable detectors of infra-red radiation and, of course, other types of radiation require suitable detectors therefor.

The cam 21a forms a part of a ctun assembly 21 which includes a shaft 21b journalled in the base 10 and carrying a gear 210 which meshes with a pinion 22a carried by a shaft 22b, this shaft being geared to an electrical servo-motor 22c mounted on heat insulating blocks, not shown, at the upper side of the base 1t). The last-mentioned parts make up a motor assembly 22. The gear 210 also meshes with a pinion 23a carried by a shaft 23b which actuates the contactor of a potentiometer 23c mounted at the top of the base 10, these parts making up a potentiometer assembly 23.

Referring now to Figure 4, it will be radiation detectors 17e, 17 are connected in opposition by conductors 24 and 25 so as to produce a resultant voltage proportional to the difference in intensity of the radiation beams incident upon the two detector units. The voltage appearing between leads 24, 25 is amplified by a unit 26 whose output is fed to the motor 22c, the

noted that the motor being mechanically connected, as described, to the contactor of potentiometer 230.

In the operation of the analyzer as thus far described, the mirror assemblies and detector units are so adjusted that equal amounts of light fall upon the respective detector units when there is a desired relationship between the refractive indices of the fluids in the chambers 13r, 13s of cell unit 13. Ordinarily, this relationship holds when the refractive indices of the two fluids are equalf In this condition, the resultant voltage produced by the detector units is zero, and no current is fed to motor 22c. Assuming that the refractive index of the fluid in chamber 13r changes so as to shift the radiation beam in a direction such that more radiation falls upon cell 17c than upon cell 17 a voltage of one polarity is produced by the interaction of the radiation detectors 17e, 17 This voltage is amplified by the unit 26 and fed to motor 220. The resulting movement of motor 22c, pinion 22a, gear 210, and cam 21a causes arm 14 to move in a clockwise direction, Figure 1, thereby producing a shift in position of the beam such that less radiation is incident upon radiation detector 17e than upon radiation detector 17 This movement continues until equal amounts of radiation are incident upon the two detectors, at which time movement of the motor is stopped. The extent of movement of the her 131' varies in such fashion as to cause more radiation to impinge upon detector 17 than upon detector 172, an opposite effect occurs, the voltage produced between conductors 24, being of opposite polarity and thus causing the arm 14 of assembly 14 to swing 'a counterclockwise direction, Figure 1. This produces a shift of the radiation beam in a direction such that less radiation falls upon detector 17 and more radiation falls upon detector 17a, the resulting movement of gear 216, motor 220 and the arm of potentiometer 230 being proportional to the extent of deviation. It will be apparent, therefore, of motor 220 and the position of the arm of potentiometer the difference in refractive index of the fluids in chambers 131', 13s and the potential appearing across this potentiometer is directly this dilference in refractive index.

system is extremely sensitive since the rotation of mirror assembly 14 produces a linear shift in the radiation beam incident upon the detector assembly 17, this linearity resulting from the fact that the mirror 14d is positioned close to the cell 13. These results are superior to moving the detector assembly itself in effect, amplified by a factor proportional to the length of the optical path formed by mirrors 15c and 16c.

In accordance with the invention, it also circuit for adjusting the sensitivity corder upon which the described variations in refractive index are recorded. To this end, I provide a constant current power supply which produces a constant current through conductor 27. This current is produced by power supply which includes a transformer 29 having its prirn'ary winding connected in circuit with an alternating current source 3E and a switch 31, the secondary winding being connected in circuit with a rectifier 32, filter impedances 33, 34, 35, 36, filter condensers 37, 38 39 and a voltage regulator tube 40. The positive term nal 41 of this constant voltage power supply is connected to conductor 27 by a resistance 42 of high ohmic a constant current flows The conductor 27 is connected through variable resistance 43 to a lead 44, the fixed terminals of potentiometer 23c being connected to leads 23 and id, respectively. A potentiometer 45 has its fixed terminals connected to leads 28 and 44-, respectively, the contactor of this potentiometer being connected by a lead 46 to one input terminal of a recorder 47, the other input terminal potentiometer 230. also connected to the arm of a switch 48a having a series of fixed terminals 49 with fixed resistances 50 connected in shunt with each pair of adjacent fixed terminals. One end of the series of fixed terminals thus formed is connected through a fixed resistance 51 to the lead 28.

In the operation of the circuit of Figure 4, potentiometer 45 controls the reference voltage at one side of the input circuit of recorder 47 so that adjustment of this potentiometer shifts the zero point of the recording upon the tape, the variations in potential at conductor 43 responsive to changes in refractive index of the fluid in chambers 132', 135 being recorded with respect to the reference voltage established at conductor 46. Adjustment of the arm of switch 43a produces changes in range or sensitivity of the recorder. in this connection, it will be noted that fixed resistors 51 51 are of low the current flow also is decreased which results in a lower voltage of potentiometers 23c and minals or" potentiometers voltage drop increases the assembly, parts similar to the cell assembly of Figure 3 being indicated by like reference characters. sembly, this lens being secured in position by an end cap 113b secured to member 13f as by screws, one of which is shown at 1130. The cell assembly further includes a heat exchanger coil outside the blocks through tends to maintain the cell at a constant temperature. If desired, the heat exchanger coil 113d may be formed by boring suitable passages through the blocks 13c and 13 The purpose of the lens i13a, to produce a convergence of the light beam passing therethrough so that such beam falls upon a more restricted portion of the Figure 4. This is well illustrated in the figure wherein the following of the beam produced by mirrors 15c and has been omitted for clarity, and it will be noted that the light beam extends each side of the junction between the cells 17.2 and 17] rather than falling upon a relatively large cells as in Figure 1. If the index of refraction of the fluid in cell 13r is greater than that of cell 13s, the beam is deflected upwardly, thereby causing the mirror to swing in a counterclockwise direction to center the beam upon the cells 172 and 17], such rotation of the mirror operating potentiometer 23 in the manner previously described to produce an indication representative of the difference in indices of refraction. Conversely, if the index of refraction of the fluid in cell 13r is less than that in cell 13s, the beam is conductors 24, 25 being the opposite terminals of the bridge.

tieularly suitable for use with infra-red radiation wherein the cells 135, 136 can .be bolometers. However, the described photoconductive cells may be any other type wherein the ohmic resistance of the cell varies with changes in intensity of the radiation incident thereon.

The circuit of Figure 7 is also suitable for use with photoemissive cells wherein a treated cathode mounted in a glass envelope emits electron under the action of radiation, these electrons being collected at an anode. Such tubes may be vacuum tubes or they may be gas filled. It will be understood, therefore, that the resistances 135 and 131-6 may represent photoernissive cells.

While the invention has been described in connection with present, preferred embodiments thereof, it is to be understood that this description is illustrative only and is not intended to limit the invention.

I claim:

1. An electrical circuit for controlling the sensitivity of a recorder having an electrical input circuit which comprises, in combination, a recorder, a voltage source, a first potentiometer having its end terminal connected across said voltage source, the contactor of said first potentiometer being connected to one input terminal of said recorder, 21 second potentiometer having its end terminals connected across said voltage source, the contactor of said second potentiometer being connected to the second input terminal of said recorder, and means for vary ing the setting of the contactor of said first potentiometer in accordance with the magnitude of the quantity to be recorded, the setting of said second potentiometer determining the zero level of signals fed to said recorder.

2. An electrical circuit for controlling the sensitivity of a recorder having an electrical input circuit which comprises, in combination, a recorder, a voltage source, a first potentiometer having its end terminals connected across said voltage source, the contactor of said first potentiometer being connected to one input terminal of said recorder, a second potentiometer having its end terminals connected across said voltage source, the contactor of said second potentiometer being connected to the second input terminal of said recorder, means for varying the setting of the contactor of said first potentiometer in accordance with the magnitude of the quantity to be recorded, the setting of said second potentiometer determining the zero level of signals fed to said recorder, and means for varying the voltage impressed across the end terminals of said first and second potentiometers.

3. An electrical circuit for controlling the sensitivity of a recorder having an electrical input circuit which comprises, in combination, a recorder, a voltage source, a resistance of high ohmic value having one terminal thereon connected to the first output terminal of said voltage source whereby substantially a constant current flows through said resistance element, a first potentiometer having one end terminal thereof connected to the second terminal of said resistance element and having the second end terminal thereof connected to the second output terminal of said voltage source, a second potentiometer having one end terminal thereof connected to the second terminal of said resistance element and having the second end terminal thereof connected to the second output terminal of said voltage source, the contactors of said first and second potentiometers being connected to the respective terminals of the input circuit of said recorder, and means for varying the setting of said first potentiometer in accordance with the magnitude of a quantity to be recorded, the setting of the contactor of said second potentiometer determining the zero level of signals fed to said recorder.

4. An electrical circuit for controlling the sensitivity of a recorder having an electrical input circuit which comprises, in combination, a recorder, a voltage source, a resistance of high ohmic value having one terminal thereof connected to the first output terminal of said voltage source whereby substantially a constant current flows through said resistance element, a first potentiometer having'one' end terminal thereof connected to the second terminal of said resistance element and having the second end terminal thereof connected to the second output ter-. minal of said voltage source, a second potentiometer hav-' ing one end terminal thereof connected to the second terminal of said resistance element and having the second end terminal thereof connected to the second output terminal of said voltage source, the contactors of said first and second potentiometers being connected to the respective terminals of the input circuit of said recorder, a variable resistance of low ohmic value as compared to the ohmic value of said first-mentioned resistance, said variable resistance being connected in shunt with the end terminals of said first and second potentiometers, and means for varying the setting of said first potentiometer in accord-' ance with the magnitude of a quantity to be recorded, the setting of the contactor of said second potentiometer determining the zero level of signals fed to said recorder.

5. An electrical circuit for controlling the sensitivity of a recorder having an electrical input circuit which comprises, in combination, a recorder, a voltage source, a resistance of high ohmic value having one terminal thereof connected to the first output terminal of said voltage source whereby substantially a constant current flows through said resistance element, a first potentiometer having one end terminal thereof connected to the second terminal of said resistance element and having the second end terminal thereof connected to the second output terminal of said voltage source, a second potentiometer having one end terminal thereof connected to the second terminal of said resistance element and having the second end terminal thereof connected to the second output terminal of said voltage source, the contactors of said first and second potentiometers being connected to the respective terminals of the input circuit of said recorder, a switch having a movable arm and a plurality of fixed contacts, a lead connecting the arm of said switch to the second terminal of said resistance element, a plurality of resistors of low ohmic value as compared to the ohmic value of said resistance element, said resistors being connected between adjacent ones of said fixed contacts, means connecting the end one of said fixed contacts to the second output terminal of said voltage source, and means for varying the setting of said first potentiometer in accordance with the magnitude of a quantity to be recorded, the setting of the contactor of said second potentiometer determining the zero level of signals fed to said recorder.

6. An electrical circuit for recording the differential intensity of two beams of radiation comprising, in combination, a recorder, a pair of radiation sensitive detectors, an amplifier, means connecting said detectors in opposition to the input terminals of said amplifier whereby the signal applied to said amplifier is representative of the difference in intensity of radiation impinging upon said pair of detectors, a servo-motor connected to the output terminals of said amplifier, a voltage source, a first potentiometer having its end terminals connected across said voltage source, the contactor of said first potentiometer being connected to one input terminal of said recorder, a second potentiometer having its end terminals connected across said voltage source, the contactor of said second potentiometer being connected to the second input terminal of said recorder, and means connecting the contactor of said first potentiometer to said servo-motor whereby rotation of said motor varies the setting of the contactor of said first potentiometer in accordance with the difference in intensity of radiation impinging upon said pair of detectors, the setting of the contactor of said second potentiometer determining the zero level of signals fed to said recorder.

7. The combination in accordance with claim 6 wherein said pair of radiation sensitive detectors comprise photovoltaic cells.

8. The combination in accordance with claim 6 wherein said radiation sensitive elements comprise temperature sensitive resistance elements positioned in adjacent arms of the diiference in magnitude of radiation impinging of a Wheatstone bridge circuit, the output terminals of upon said pair of detectors, a servo motor connected to said bridge circuit being connected to the input terminals the output terminals of said amplifier, a voltage source, of said amplifier. a potentiometer having its end terminals connected across 9. An electrical circuit for recording the differential said voltage source, means connecting the contactor of intensity of two beams or radiation comprising, in comsaid potentiometer to one input terminal of said recorder, blnation, a recorder, a pair of radiation sensitive detecmeans connecting one end terminal of said potentiometer tors, an amplifier, means connecting said detectors in to the second input teiminal or said recorder, and means by the signal applied to said amplifier is representative of contactor of said potentiometer whereby the voltage apthe difference in intensity of radiation impinging upon plied to said recorder is a function of the rotation of said pair of detectors, a servo-motor connected to the said motor, which in turn is a function of the diiference output terminals of said amplifier, a voltage source a in the radiation impinging upon said pair of detectors resistance of high ohmic value having one terminal there 11 An electrical circuit for recording the diiferential through said resistance element, a first potentiometer tectors, an ampliner, means connecting said detectors having one end terminal thereof connected to the secin opposition to the input terminals of sa d amplifier ond terminal of said resistance element and having the whereby the signal applied to said amplifier 1S representasecond end terminal thereof connected to the second outtive of the difference in intensity of radiation impinging put terminal of said voltage source, a second potentiomupon said pair of detectors a servo motor connected to eter having one end terminal thereof connected to the the output terminals of said amplifier a voltage source second terminal of said resistance element and having a resistance of high ohmic value having one terminal the second end terminal thereof connected to the second thereof connected to the first output terminal of said output terminal of said voltage source, the contactors of voltage source, a potentiometer having one end terminal said first and second potentiometers being connected to thereof connected to the second terminal of said rethe respective terminals of the input circuit of said resistance element and having the second end terminal corder, a variable resistance of low ohmic value as comthereof connected to the second output terminal of said pared to the ohmic value of said first-mentioned resistance, voltage source means connecting the contactor of said said variable resistance being connected in shunt with the potentiometer to one input terminal of said recorder, end terminals of said first and second potentiometers, means connecting said second end terminal of said poand means connecting the contactor or said first potentitentiometer to the second input terminal of said recorder, ometer to said servo-motor whereby rotation of said and means connecting the diive shaft of said servo motor potentiometer in accordance with the difference in intensity of radiation impinging upon said pair of detectors, References Cited in the file of this patent UNITED STATES PATENTS 10. An electrical circuit for recordin the differential ggzgs I intensity f W ams of radiation comprising, in com- 1465214 Foreste; A -14 1923 n n, a r c rder, a pair of radiation sensitive detec- 2,065,365 DO I {I 1936 r an mplifier, means connecting said detectors in 2358103 R 3' e S 1944 pp i ion to the input terminals of said amplifier where- 14 y P 5 y he signal applied to said amplifier is representative 1 s i 

